Shoes soles, in particular midsoles, are usually manufactured from polymers such as ethylene-vinyl acetate (EVA). A standard manufacturing process for such polymers comprises injection molding the sole material into a conventional sole mold.
As the requirements on shoe soles, in particular for sport shoes, become more challenging in order to provide improved performance properties, in particular enhanced cushioning properties, new sole materials have been developed. For example, applicant disclosed in EP 2 786 670, EP 2 767 183, EP 2 767 181, EP 2 845 504 deformation elements for shoe soles comprising a plurality of randomly arranged particles.
However, conventional molds for molding a shoe sole are not adapted to the specific requirements when molding a shoe sole made from particles. For example, the particle molding process with a conventional mold requires a large amount of energy for heating the mold, as conventional molds typically have a high mass. Moreover, the cooling process of such molds is slow and therefore leads to extended cycle times. Finally, molding soles from particles requires to uniformly supplying a gaseous or liquid medium to the particles in order to achieve a homogeneous interconnection of the particles. Conventional molds are not adapted to such a uniform medium supply.
The US 2008/0277837 discloses gas permeable molds and mold segments having open porosity. Blind vents in the mold wall's outside surface allow for an uninterrupted molding surface while enhancing the gas permeability provided by the open porosity. Methods of making such gas permeable molds include forming them from laser-sintered materials. Other molds are known from US 2007/0029698, US 2013/0333950, US 2001/0048182, U.S. Pat. Nos. 5,937,265 and 5,518,060.
Further prior art is disclosed in DE 10 2013 002 519 A1, DE 10 2007 054 723 B4, DE 10 2004 028 462 A1, DE 197 04 700 C1, DE 10 2014 107 847 A1, EP 2 684 665 A2 and DE 10 2009 030 678 A1.
Therefore, the underlying problem of the present invention is to provide a sole mold that is capable to at least partly overcome the above-mentioned deficiencies of conventional sole molds for molding shoe soles from particles.